Search

Knitted structure based on through‐silicon vias is utilized to realize the miniaturization of frequency‐selective rasorber (FSR). According to equivalent circuit model analysis, additional inductance and capacitance introduced by an array of metal vias are considered, which is combined with lossy cross‐frame and lossless double square‐loop structure to realize the function of FSR. Through full wave simulation, the proposed 2.5‐D FSR demonstrates one passband between two absorption bands. The simulated results indicate a significant size reduction with P = 0.15 λL, where λL is the free‐space wavelength at the lowest frequency of ‐10 dB reflection. Moreover, an insertion loss of 0.49 dB can be observed at 3.99 GHz, the fractional bandwidth for reflection coefficients less than ‐10 dB is 100%, and the thickness of the whole structure is 0.138 λL, respectively. In addition, the frequency response of this miniaturized FSR is stable for incident angle up to 40° and both linear polarizations. After then, the prototype of this 2.5‐D FSR is fabricated and measured, which shows reasonable agreement with simulated results. [ABSTRACT FROM AUTHOR]

A metasurface‐based substrate integrated Fabry‐Pérot cavity (FPC) antenna is presented for improved radiation performance associated with the low profile. A novel partially reflective planar (PRS) artificial magnetic conductor (AMC) structure is proposed as the upper reflector of the substrate integrated FP resonant cavity. A microstrip patch antenna is embedded inside the cavity as a feed. The proposed antenna is designed to operate at 9.35 GHz with the maximum realized gain of 14.2 dBi and the overall profile of λ0/10 (λ0 is the operating wavelength in free space). The low‐profile performance of the proposed design outperforms any previous substrate‐integrated FPC antenna design with this gain performance. The influences of the FP cavity on the reduction of the antenna profile and the enhancement of the antenna gain are also investigated. Good agreement between the measured and simulated results validates the feasibility of the analysis and design approach. [ABSTRACT FROM AUTHOR]

In order to obtain the higher propagating efficiency in the photonic crystal waveguide, in this paper, a two-dimensional photonic crystal waveguide composed of Kerr nonlinear dielectric rods is considered to study the parameters influence on transmittance. The most sensitive factor on transmittance is obtained by the method of (NFDTD) according to the orthogonal numerical analysis, which may be helpful to the nonlinear Kerr medium selection in the photonic crystal waveguide design. [ABSTRACT FROM AUTHOR]

Tunable absorption in periodic structure composed of graphene-based hyperbolic metamaterials (GHMMs) and isotropic medium is investigated by the transfer matrix method. The parallel part for relative permittivity of GHMMs consisting of monolayer graphene and conventional dielectric can be tuned by the chemical potential and dielectric layer thickness. The real part of the group index of GHMMs is insensitive to incident angle at the required frequency and the absorption of the periodic structure with GHMMs can be obtained nearly 100% at 22.4 terahertz (THz). The absorption peak of this frequency is almost uniform for both transverse electric (TE) and transverse magnetic (TE) polarizations. However, a new absorption peak can be observed incident angle is larger than 40 degree for TM polarization from 10 to 30 THz. The research results show that the absorption is insensitive to electromagnetic polarization at certain frequency. A new absorption peak can be found with TM polarization in low frequency region. These novel and effective GHMMs can replace metallic thin films as polarizing beam splitter for future optoelectronic applications. [ABSTRACT FROM AUTHOR]

• Sustainable SCC made with recycled concrete aggregate and fly ash, slag, silica fume. • Using 50% and 100% RCA declined the compressive and splitting tensile strength. • Using a combination of fly ash, slag, silica fume improved the mechanical properties. • Shrinkage of RA-SCC increases with an increase in RCA content. • SCC with high volumes of SCM had higher resistance to freezing and thawing. This research aims to maximize the content of supplementary cementitious material (SCM) and recycled concrete aggregate (RCA) in self-compacting concrete (SCC) by using a combination of fly ash, slag and silica fume. A sustainable SCC was proposed by substantially substituting natural aggregates with RCA and cement with SCM. A total of 23 mixes, including binary, ternary and quaternary mixes were prepared. Binary mixes were prepared with fly ash and ternary mixes were prepared with fly ash and slag. Quaternary mixes were blended with fly ash, slag, silica fume. The mechanical and durability properties were studied. The effect of RCA and SCM was investigated as well as using a combination of fly ash, slag and/or silica fume. The test results indicate that the proposed combination of fly ash, slag and silica fume can compensate for the detrimental effect of RCA and significantly improve the mechanical and durability properties of SCC with RCA, thus optimize the sustainability performance of SCC by minimizing cement and natural resources content. [ABSTRACT FROM AUTHOR]

Micron-sized Si anodes garner renewed attention due to their advantages of low cost, small specific surface area, and high energy density. However, micron-sized Si anodes undergo significant volume changes during lithiation/delithiation, leading to particle cracking and pulverization. This study employs the tape casting method and ultrafast high-temperature sintering technology to construct a porous sheet, within which a solid framework constrains the Si particles. In rate performance tests, when the current density rises to 1 A g -1 , the micron-sized Si in the porous sheet demonstrates a delithiation capacity of 2145 mAh g -1 , compared to 113 mAh g -1 for the pristine Si, showing efficient ion and electron conductive pathways in the framework. When cycled at 0.3 A g -1 , the delithiation capacity of the ball-milled micron-sized Si in the porous sheet is 1496 mAh g -1 after 100 cycles, in contrast to 95 mAh g -1 for the pristine Si. The enhanced cycling stability of Si in the porous sheet results from the strong mechanical constraint imposed by the solid framework, which suppresses volume changes, inhibits particle cracking, and reduces solid electrolyte interphase growth. This strategy of constructing porous sheets and utilizing solid-solid bonding to constrain Si particles represents a novel approach for Si anode modification., (© 2024 Wiley‐VCH GmbH.)

The positive electrode|electrolyte interface plays an important role in all-solid-state Li batteries (ASSLBs) based on garnet-type solid-state electrolytes (SSEs) like Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO). However, the trade-off between solid-solid contact and chemical stability leads to a poor positive electrode|electrolyte interface and cycle performance. In this study, we achieve thermodynamic compatibility and adequate physical contact between high-entropy cationic disordered rock salt positive electrodes (HE-DRXs) and LLZTO through ultrafast high-temperature sintering (UHS). This approach constructs a highly stable positive electrode|electrolyte interface, reducing the interface resistance to 31.6 Ω·cm 2 at 25 °C, making a 700 times reduction compared to the LiCoO 2  | LLZTO interface. Moreover, the conformal and tight HE-DRX | LLZTO solid-state interface avoids the transition metal migration issue observed with HE-DRX in liquid electrolytes. At 150 °C, HE-DRXs in ASSLBs (Li|LLZTO | HE-DRXs) exhibit an average specific capacity of 239.7 ± 2 mAh/g at 25 mA/g, with a capacity retention of 95% after 100 cycles relative to the initial cycle-a stark contrast to the 76% retention after 20 cycles at 25 °C in conventional liquid batteries. Our strategy, which considers the principles of thermodynamics and kinetics, may open avenues for tackling the positive electrode|electrolyte interface issue in ASSLBs based on garnet-type SSEs., (© 2024. The Author(s).)

This paper presents the design and numerical investigation of a graphene-based switchable terahertz (THz) metasurface for ultrawideband absorption and multiband cross polarization conversion. The device's operational mode can be altered to absorption or reflection by using the electrostatic capabilities exhibited by graphene. The numerical calculations yield results indicating that in absorption mode, it maintains a bandwidth ratio of 152% within the frequency range of 1.04-7.74 THz. In polarization conversion mode, the design demonstrates the ability to convert linearly polarized and circularly polarized waves to their respective cross-polarization states within the frequency ranges of 1.8-2.5 THz, 3.5-4.1 THz, and 5.6 THz. Moreover, calculated results indicate that linear-to-circular conversion can be realized at 2.64, 3.45, and 5.4 THz frequencies. In addition, the absorption and polarization conversion ratio parameters were analyzed using the multiple reflection theory, which demonstrated significant agreement with the simulation results. The designed metasurface exhibits significant potential in the field of terahertz devices, including stealth technology, smart switches, and other related applications.

This paper proposes a functionally reconfigurable integrated structure of a Fabry-Perot (FP) antenna and wideband liquid absorber. First, a two-layer partial reflecting surface (PRS) has been designed. Then, a patch antenna is used to act as the source antenna. By combining the source antenna with the PRS, an FP antenna has been designed. What's more, taking full advantage of the reflective properties of PRS, a liquid broadband absorber is then designed. Last, the integrated structure with two functions has been realized. It can be used as the FP antenna or the liquid absorber through the extraction and injection of ethanol. In this way, it is effective to switch between stealth and detection states which can be used in different electromagnetic environments. The PRS is elaborately tailored to serve as both a component of the FP antenna and the metal ground of the broadband liquid absorber. Then the integrated structure is realized by combining the FP antenna with the liquid absorber. The PRS is composed of patches on the top layer of the substrate and the square loop on the bottom. The liquid absorber is composed of a 3-D printed container, 45% ethanol layer and the PRS is used to serve as the metal ground. The formula of Mie resonance theory has been extended and used to design the liquid absorber. The gain of the antenna is 19.7 dBi when the ethanol is extracted. When the ethanol is injected, a wideband liquid absorber is achieved. The absorption band (S 11  < - 10 dB) ranges from 4 to 18 GHz. The absorption bandwidth is over 133%. The monostatic RCS reduction bands of the structure with ethanol range from 4 to 18 GHz and the average RCS reduction is 28.4 dBsm. The measured and simulated results are in good agreement., (© 2023. Springer Nature Limited.)

TiO 2 is a popular photocatalyst due to its low cost and easy availability. Herein, we for the first time synthesized carbon coated TiO 2 nano-dendrites (C-TiO 2 NDs) using a simple hydrothermal method without high-temperature sintering, in which citric acid is used as an adjuvant. This unique dendritic structure consisting of a single small hexagonal piece greatly increases the BET specific area (116.386 m 2  g -1 ) and pore size (0.418 cm 3  g -1 ), increasing the photocatalytic active site and facilitate efficient capture of light. Besides, compared with the TiO 2 nanobelts (NBs) prepared by sintering method, the surface of C-TiO 2 NDs prepared by hydrothermal method with citric acid are coated with carbon layers, which make C-TiO 2 NDs exhibit stronger photocatalytic hydrogen evolution performance under simulated solar light irradiation due to the presence of carbon coatings promoting electron-hole separation and absorbing NIR light., Competing Interests: Declaration of Competing Interest The authors declare that we have no conflicts of interest to this work., (Copyright © 2020 Elsevier Inc. All rights reserved.)